Change from 4.1 to 3.9 diff

Spartacus · November 04, 2006, 12:11:41 AM

Hi,
Anyone know what\'s involved in changing from a 4.1 ratio diff to the autos 3.9. Do you need to change the whole case and drive shaft or just the internals? If so does it then need to be shimmed etc?

ScuttleRX · November 04, 2006, 12:16:43 AM

Ive always wondered how much of a job this is, are you going for a top speed monster? or just better mpg on the motorway

Spartacus · November 04, 2006, 12:22:03 AM

Quote from: ScuttleRXIve always wondered how much of a job this is, are you going for a top speed monster? or just better mpg on the motorway

mmmmm no just doing a bit of research for a possible conversion that would mean I\'d have an engine that wouldn\'t be happy reving over 6k

ScuttleRX · November 04, 2006, 12:24:32 AM

Ah I see, keep toying with the idea of going the other way 4.1 ----> 4.3, but think there are more cost effective and essential things for mine before that.

What engine are you thinking of going for? or is it hush hush for now

Spartacus · November 04, 2006, 12:29:33 AM

Quote from: ScuttleRXWhat engine are you thinking of going for? or is it hush hush for now

If I go for it, LS1 or LS2 V8 but it\'s a while off yet if at all.

BlitzBoy · November 04, 2006, 12:31:39 AM

just the final drive ring gear, take the diff case off the car then unbolt the casing then u can see the diff inside with the ring gear bolted to it, there are two bearings you have to prize off first and some shims, took my mechnic an hour and half to do with the proper tools to change the diff, in this case you will be just swapping out the ring gear

Rotary_Menace · November 15, 2006, 03:52:41 PM

is it me or are more and more people in the uk contemplating the LSX swap, go for it, the hinson supercars subframe for RHD is going to be availiable soon (so i hear) will make things very easy.

Spartacus · November 15, 2006, 04:03:26 PM

Been on swapcartech?

Rotary_Menace · November 15, 2006, 04:15:11 PM

Yep, you rhdv8

Spartacus · November 15, 2006, 04:17:10 PM

Yup it may seem that theres alot of interest or it could be just me getting about alot lol

Rotary_Menace · November 15, 2006, 04:24:41 PM

I know what you mean, its a case of look but dont touch for me at the min. cant wait to see one in person. I think the LS2 is the way to go over the LS1 bit of extra work but cant beat cubes if FI is not a viable option, some people have even got ls7\'s running in there FD\'d

Spartacus · November 15, 2006, 04:39:09 PM

As my goal isn\'t all out power, if I go for it I\'d go LS1 first, see how it goes then if needed you can always add cubes.

tinker-27 · December 07, 2006, 11:46:25 PM

the easiest way to swap to 3.9 from 4.1 is to just fit the whole auto diff (3,9) all you have to do is swap the drive flange on the front for the manual one . i use a 3.9 in my ls powered fd and its better than the 4.1 but with the 6 speed the gearing is good anyway 70mph=1700rpm which is very relaxed. a ls1 with a cam and set up properly is good for 400+bhp about the same as ls2 and for a lot less money ,the ls2 also comes with fly by wire throttle etc. if you are going to buy a ls just make sure its a 2001 on as they are better . just ordered my 7.0 litre short motor rool on next year !!!

Crazy Eddie · December 08, 2006, 12:45:28 AM

Sorry for Hijack but any chance of seeing pics of your car Tinker (or in person if only in Birmingham)
I am really considering this option when / if my engine blows.
Cheers
Eddie

stylus350 · December 08, 2006, 09:18:55 AM

Quote from: Crazy EddieSorry for Hijack but any chance of seeing pics of your car Tinker (or in person if only in Birmingham)
I am really considering this option when / if my engine blows.
Cheers
Eddie

If he takes you out - put your seatbelt on! He likes going sideways, even in a straight line. Obviously very much in control though :cool